A NEWLY DEVELOPED FLUORESCENCE MODEL FOR C2H6 Delta n5 AND APPLICATION TO COMETARY SPECTRA ACQUIRED WITH NIRSPEC AT KECK II

Accurate rotational temperatures are essential for extracting production rates for parent volatiles in comets. Two strong bands of ethane ( Delta *n7 at 2985.39 cm--1 and Delta *n5 at 2895.67 cm--1) are seen in infrared cometary spectra, but the Q-branches of Delta *n7 are not resolved by current in...

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Published in:The Astrophysical journal 2011-03 (2), p.jQuery1323910442755='48'-jQuery1323910442755='48'
Main Author: Radeva, Yana L
Format: Article
Language:English
Online Access:Get full text
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Summary:Accurate rotational temperatures are essential for extracting production rates for parent volatiles in comets. Two strong bands of ethane ( Delta *n7 at 2985.39 cm--1 and Delta *n5 at 2895.67 cm--1) are seen in infrared cometary spectra, but the Q-branches of Delta *n7 are not resolved by current instruments and cannot provide an accurate rotational temperature with current models. We developed a fluorescence model for the C2H6 Delta *n5 band that can be used to derive a rotational temperature. We applied our C2H6 Delta *n5 model to high-resolution infrared spectra of the comets C/2004 Q2 Machholz and C/2000 WM1 (LINEAR), acquired with the Near-infrared Echelle Spectrograph on the Keck II telescope. We demonstrate agreement among the rotational temperatures derived from C2H6 Delta *n5 and other species, and between mixing ratios derived from C2H6 Delta *n5 and C2H6 Delta *n7. As a symmetric hydrocarbon, C2H6 is observed only in the infrared, and it is now the fifth molecule (along with H2O, HCN, CO, and H2CO) for which we can derive a reliable rotational temperature from cometary infrared spectra.
ISSN:0004-637X
DOI:10.1088/0004-637X/729/2/135